Plasma Free Amino Acid Concentrations Research Articles

Micellar casein and sodium caseinate supramolecular structure differently impacts subsequent food intake in pigs.

Dietary protein reduces energy intake in following meals by signaling directly or indirectly to the brain. We recently observed differences in plasma amino acid kinetics and intra-gastric behavior between micellar casein (MC) and sodium caseinate (SC) in pigs, two factors that impact food intake. Our objective was to clarify whether the supramolecular structure of casein, given as a preload to pigs, impacts on subsequent food intake. Overnight fasted pigs were allowed to consume casein drinks differing in casein macromolecular structure (SC vs MC) within 5min in a cross-over study. Ad libitum intake of their regular feed was assessed during 1h, either 1 or 4h after casein drink ingestion. To evaluate the potential mechanisms at play, gastric emptying of the casein drinks radiolabeled with 99Tc-colloïd was followed using gamma-scintigraphy while plasma kinetics of ghrelin, GLP-1, insulin and free amino acids were evaluated. The amount of feed consumed 1, but not 4h, after SC ingestion was lower than the amount of feed consumed after MC ingestion (P=0.03). Gastric emptying parameters, plasma ghrelin, GLP-1 and insulin kinetics after both types of casein ingestion were not significantly different (P>0.05). However, plasma free amino acid concentrations, known to reduce food intake, increased after both SC and MC ingestion but was greater after SC than MC ingestion from 60 to 120min (P=0.009). In conclusion, casein supramolecular structure in a preload drink impacts differently subsequent energy intake, likely due to difference in amino acid bioavailability. Micellar casein exhibits less anorectic effect than sodium caseinate, a property that could benefit population with high protein need but low appetite such as elderly.

Quantification and evaluation of plasma free amino acid concentrations by LC-MS/MS after total gastrectomy

The effect of total gastrectomy (TG) on plasma free amino acid (PFAA) concentrations in patients with stage II gastric cancer was investigated in the study. Nineteen patients' plasma samples were collected before and three months post-gastrectomy, and PFAA levels were quantified using LC-MS/MS. For gradient elution of amino acids, the mobile phases (A: 3% formic acid-5% methanol-30 mM ammonium formate, B: acetonitrile) and a Hypersil C18 column (100 mm x 2.1 m, 1.9 µm) were used. The findings revealed substantial modifications in the profile of PFAA after TG. In particular, the concentrations of twenty amino acids increased significantly, including branched-chain amino acids, L-glutamate, L-alanine, L-methionine, glycine, L-cystine, and L-histidine. Conversely, L-arginine was also reduced statistically. These alterations in the PFAA profile indicate the favorable effects of TG on various physiological processes, such as enhanced immune function, improved tissue healing, and increased energy production. Investigating the effects of various surgical techniques on PFAA profiles is a promising approach for optimizing surgical procedures, improving metabolic function, increasing immunological responses, and improving overall quality of life. These findings highlight the significance of evaluating amino acid metabolism as an important part of treatment, given its potential to improve clinical outcomes and general well-being.

Plasma-free Amino Acid Profile is Beneficial for Breast Cancer Screening in Women With Dense Breasts

BackgroundAminoIndex™ Cancer Screening (AICS breast) was developed as a breast cancer screening test using multivariate analysis of plasma free amino acid (PFAA) profiles. This study investigated the relationship between the AICS breast rank and breast density on mammography (MMG) for the detection of breast cancer. Materials and MethodsMMG and blood samples were obtained preoperatively from 224 patients with breast cancer who did not receive neoadjuvant chemotherapy between 2017 and 2019. PFAA concentration was measured using liquid chromatography-mass spectrometry, and the AICS breast and AICS ranks were calculated. Detection rates were compared between MMG (categories 3-5) and AICS breasts (ranks B and C) according to breast density. ResultsBreast density was classified as extremely dense in 9.4%, heterogeneously dense in 48.2%, scattered in 29.9%, and fatty in 12.5% of patients. Dense breasts (extremely dense and heterogeneously dense) represented 57.6%. The overall detection rate by MMG was 82.6% and significantly lower in patients with dense breasts (74.4%) compared to non-dense breasts (93.7%). The overall detection rate by AICS breast was 50.0%, with no difference between patients with dense breasts (45.7%) and those with non-dense breasts (55.8%). The combination of MMG and AICS breast increased the detection rate to 91.5% overall, 88.3% in patients with dense breasts, and 95.8% in those with non-dense breasts. ConclusionThis study demonstrated that the detection rate of AICS breast was not associated with breast density, unlike MMG. Adding AICS breast to MMG may be beneficial for breast cancer screening in patients with dense breasts.

Relationship Between Altered Plasma-Free Amino Acid Levels and Hyperuricemia in Dyslipidemia Without and With Hypertension.

Background: Investigating the association between plasma-free amino acids (PFAAs) and hyperuricemia (HU) in dyslipidemia (DL) and dyslipidemia with hypertension (DH) is crucial, as it could provide valuable insights into the pathophysiology of these conditions and contribute to the development of targeted prevention and management strategies. Therefore, in this study, we aimed to elucidate the associations between PFAAs and HU in individuals with DL and DH. Methods: We quantified PFAAs and uric acid levels among Japanese healthy subjects (n = 1311; HU, n = 57), subjects with DL (n = 1483; HU, n = 219), and subjects with DH (n = 1159; HU, n = 237). Results: The concentrations of most PFAAs showed significant differences between subjects without and with HU across all groups (p < 0.05 to 0.001). Adjusted logistic regression analyses revealed that certain PFAAs were consistently positively or negatively associated with HU across all groups. Specifically, in the DL group, alanine, tryptophan, and tyrosine showed significant positive associations with HU, while in the DH group, citrulline and glutamate exhibited similar positive associations (p < 0.05 to 0.001). Conversely, threonine in the healthy group (p < 0.05) and glutamine in the DL group (p < 0.05) demonstrated significant inverse associations with HU. Conclusions: This study revealed a potential close relationship between alterations in PFAA profiles and HU in dyslipidemia, without and with hypertension. The findings warrant further research to elucidate the role of altered amino acid and uric acid levels as potential disease biomarkers and therapeutic targets.

Multi-omics analysis-based clinical and functional significance of a novel prognostic and immunotherapeutic gene signature derived from amino acid metabolism pathways in lung adenocarcinoma.

Studies have shown that tumor cell amino acid metabolism is closely associated with lung adenocarcinoma (LUAD) development and progression. However, the comprehensive multi-omics features and clinical impact of the expression of genes associated with amino acid metabolism in the LUAD tumor microenvironment (TME) are yet to be fully understood. LUAD patients from The Cancer Genome Atlas (TCGA) database were enrolled in the training cohort. Using least absolute shrinkage and selection operator Cox regression analysis, we developed PTAAMG-Sig, a signature based on the expression of tumor-specific amino acid metabolism genes associated with overall survival (OS) prognosis. We evaluated its predictive performance for OS and thoroughly explored the effects of the PTAAMG-Sig risk score on the TME. The risk score was validated in two Gene Expression Omnibus (GEO) cohorts and further investigated against an original cohort of chemotherapy combined with immune checkpoint inhibitors (ICIs). Somatic mutation, chemotherapy response, immunotherapy response, gene set variation, gene set enrichment, immune infiltration, and plasma-free amino acids (PFAAs) profile analyses were performed to identify the underlying multi-omics features. TCGA datasets based PTAAMG-Sig model consisting of nine genes, KYNU, PSPH, PPAT, MIF, GCLC, ACAD8, TYRP1, ALDH2, and HDC, could effectively stratify the OS in LUAD patients. The two other GEO-independent datasets validated the robust predictive power of PTAAMG-Sig. Our differential analysis of somatic mutations in the high- and low-risk groups in TCGA cohort showed that the TP53 mutation rate was significantly higher in the high-risk group and negatively correlated with OS. Prediction from transcriptome data raised the possibility that PTAAMG-Sig could predict the response to chemotherapy and ICIs therapy. Our immunotherapy cohort confirmed the predictive ability of PTAAMG-Sig in the clinical response to ICIs therapy, which correlated with the infiltration of immune cells (e.g., T lymphocytes and nature killer cells). Corresponding to the concentrations of PFAAs, we discovered that the high PTAAMG-Sig risk score patients showed a significantly lower concentration of plasma-free α-aminobutyric acid. In patients with LUAD, the PTAAMG-Sig effectively predicted OS, drug sensitivity, and immunotherapy outcomes. These findings are expected to provide new targets and strategies for personalized treatment of LUAD patients.

Plasma free amino acid profiles are associated with serum high molecular weight adiponectin levels in Japanese medical check-up population without type 2 diabetes mellitus

To prevent the progression of type 2 diabetes mellitus (T2DM), early detection and intervention are important. Several studies have already shown that the serum adiponectin level could be useful for evaluating the future risk of T2DM. Recently, plasma free amino acid (PFAA) concentrations have also emerged as potential biomarkers that predict the future onset of T2DM. In this study, we aimed to further characterise PFAA profiles by elucidating the association with the serum high molecular weight (HMW) adiponectin level in this cross-sectional study. A total of 1000 Japanese subjects who underwent medical check-ups were enrolled, and their plasma concentrations of 21 amino acids and clinical parameters were measured. The subjects without T2DM were divided into quartiles (Q1-4) by serum HMW adiponectin level, and the association with between PFAA concentrations was analysed. Concentrations of glutamate, alanine, proline, tyrosine, histidine, methionine, lysine, branched-chain amino acids (BCAAs) and tryptophan varied significantly according to the adiponectin quartile. Furthermore, serum adiponectin levels showed significant inverse correlations with these amino acids. The change in the PFAA profile in the group with the lowest adiponectin concentrations (Q1) was similar to that of T2DM patients. Although both adiponectin levels and PFAA concentrations are known to be altered by the accumulation of visceral fat and insulin resistance, the levels of glutamate, BCAA, lysine and tryptophan remain significantly associated with adiponectin level after adjustment for age, body mass index and homeostasis model assessment of insulin resistance, showing the direct association between PFAA concentrations and the serum HMW adiponectin level. Registration number: University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) UMIN000029920, registered on Nov 13th 2017 (prospectively registered).

Serum protein concentration and amino acid profile of HIV/HBV co-infected subjects on HAART in Plateau State, Nigeria.

Human immunodeficiency virus (HIV) and hepatitis B virus (HBV) are currently two important blood-borne human pathogens of major public health concern with high prevalence rates in Africa. The study assessed the impact of HIV and HBV mono- and co-infections on serum total protein, albumin, globulin fractions and plasma free amino acids concentrations. This was a cross-sectional study on adult (25 - 64 years old) patients on Highly Active Antiretroviral Therapy attending AIDS Preventive Initiative in Nigeria Centre, Jos University Teaching Hospital, Plateau State, Nigeria. It involved 80 subjects; 20 HIV/HBV co-infected, 20 each of HIV and HBV mono-infected controls, and 20 seronegative controls. Significant (p<0.05) increases in total protein and gamma globulin but a reduction in albumin concentrations were observed in the HIV/HBV co-infected group. Similarly, significant (p<0.05) increases in alpha-1 and alpha-2 globulin concentrations were observed in the mono- and co-infected groups compared to the seronegative control group. There were significant (p<0.05) increases in the glucogenic, aromatic and branched-chain amino acid concentrations of the HIV/HBV co-infected subjects. The study suggests prognostic importance of alpha and gamma globulin fractions of serum protein as well as amino acid profile in the management of HIV/HBV co-infection.

Lysine supplemented to poultry by‐product meal replacement diet modulates body growth, metabolism and related gene expressions of hybrid sturgeon (Acipenser schrenckii ♀ × Acipenser baerii ♂)

Hybrid sturgeon (Acipenser schrenckii♀×Acipenser baerii♂) were fed with four isonitrogenous (approximately 43.0%) and isolipidic (approximately 13.6%) diets: FM-based diet (lysine control diet, LC diet), poultry by-product meal totally substitute diet (lysine low diet, LL diet), LL diet supplemented lysine to match the LC diet group level (lysine medium diet, LM diet) and LL diet supplemented lysine over the LC diet group level (lysine high diet, LH diet) for 8 weeks to determinate the effect of dietary lysine supplementation on growth performance, metabolism and immunity response. The results indicated that compared with control diet, LL diet led to depressed growth performance and feed utilization. Lysine supplementation had a significant effect on improving the growth performance and feed utilization. Moreover, LL diet also decreased the plasma-free amino acid concentration, nutrient content and mRNA expression level of IGF system and increased plasma immunity indexes and gene expression level of HSP70 than the control diet. LM diet had marked efficiency to eliminate the differential effects caused by lysine insufficiency. However, high-level lysine addition had undesirable effect on regulating the growth performance, feed utilization, plasma-free amino acid concentration, nutrient content, immunity indexes and gene expression level. Present study demonstrated that poultry by-product meal with lysine addition could totally substitute FM without adverse effects on growth performance, plasma AA concentration, nutrient content and immune response in hybrid sturgeon. Our results provide a solid evidence for using lysine to improve the body growth performance and metabolism in hybrid sturgeon.

Preoperative AminoIndex Cancer Screening (AICS) abnormalities predict postoperative recurrence in patients undergoing curative resection for non-small cell lung cancer

BackgroundAminoIndex™ Cancer Screening (AICS (lung)) was developed as a screening test for lung cancer using a multivariate analysis of plasma-free amino acid (PFAA) profiles. According to the developed index composed of PFAA, the probability of lung cancer was categorized into AICS (lung) ranks A, B, and C in order of increasing risk. The aim of the present study was to investigate the relationship between the preoperative AICS (lung) rank and surgical outcomes in patients who underwent curative resection for non-small cell lung cancer (NSCLC).MethodsPreoperative blood samples were collected from 297 patients who underwent curative resection for NSCLC between 2006 and 2015. PFAA concentrations were measured. The relationship between the preoperative AICS (lung) rank and clinicopathological factors was examined. The effects of the preoperative AICS (lung) rank on postoperative outcomes were also analyzed.ResultsThe AICS (lung) rank was A in 93 patients (31.3%), B in 82 (27.6%), and C in 122 (41.1%). The AICS (lung) rank did not correlate with any clinicopathological factors, except for age. Based on follow-up data (median follow-up period of 6 years), postoperative recurrence was observed in 22 rank A patients (23.7%), 15 rank B (18.3%) and 49 rank C (40.2%). In the univariate analysis, preoperative AICS (lung) rank C was a worse factor of recurrence-free survival (p = 0.0002). The multivariate analysis identified preoperative AICS (lung) rank C (HR: 2.17, p = 0.0005) as a significant predictor of postoperative recurrence, particularly in patients with early-stage disease or adenocarcinoma.ConclusionPreoperative AICS (lung) rank C is a high-risk predictor of postoperative recurrence in patients undergoing curative resection for NSCLC.

Use of encapsulated L-lysine-HCl and DL-methionine improves postprandial amino acid balance in laying hens.

The supplementation of dietary limiting amino acids (AA) with crystalline AA makes the use of low-protein diets an option in poultry production. The differing absorption rates of crystalline and protein-bound AA may lead to temporally imbalanced AA in the postabsorptive period. In this study, two experiments were conducted to evaluate the effect of encapsulated L-lysine-HCl (L-Lys-HCl) and DL-methionine (DL-Met) on the laying performance of hens. In exp. 1, a total of 135 forty-seven-wk-old Hy-Line Brown hens were subjected to three dietary treatments for 8 wk: basal diet supplemented with 0.14% L-Lys-HCl and 0.17% DL-Met to satisfy the NRC (1994) total Lys and Met recommendation (control) and basal diet supplemented with encapsulated L-Lys-HCl and DL-Met at the levels of 60% (60CLM, 0.084% L-Lys-HCl and 0.102% DL-Met) or 80% of control (80CLM, 0.112% L-Lys-HCl and 0.136% DL-Met), respectively. In exp. 2, 24 fifty-five-wk-old Hy-Line Brown hens were individually reared in cages and subjected to the same treatments as in exp. 1. The plasma concentrations of free AA and nitrogen metabolites were measured 2, 4, and 6 h after fed. The results showed that dietary AA treatment had no significant influence on body weight (BW), feed intake, laying rate, egg weight, egg mass, or feed efficiency. The expression levels of AA transporters CAT-1, y+LAT1, b0,+AT, B0AT, rBAT, EAAT3, and PepT1 in the duodenum, jejunum, and ileum were not influenced (P > 0.05) by dietary treatment. There was an interaction of dietary AA treatment and time (P < 0.05) and the 80CLM hens exhibited higher concentrations of Lys (P < 0.05) than the controls at 2-h time point. In contrast, plasma Met concentration was not influenced (P > 0.05), while Cys was reduced in the 60CLM hens at every time point. The 80CLM hens had higher taurine concentrations than those receiving the control diet at every postprandial time point. In conclusion, these findings demonstrate that by using encapsulated form, the supplemental levels of synthetic L-Lys-HCl and DL-Met can be effectively reduced by approximately 20% with no negative effect on laying performance. The result suggests that encapsulated Lys and Met may ameliorate the postabsorptive AA balance and contribute to the reduced dietary AA supplemental levels.

Encapsulated crystalline lysine and DL-methionine have higher efficiency than the crystalline form in broilers

Crystalline amino acids (AAs) exhibit high nutritional values when supplemented AA-deficient diets. However, the AAs in crystalline form in the diet are absorbed quickly than protein-bound AAs, which may take an effect on AA utilization efficiency. In this study, 2 experiments were conducted to investigate the effect of encapsulated lysine-HCl (Lys) and DL-methionine (DL-Met) on the growth performance of broiler chickens. In experiment 1, a total of 432 one-day-old male Arbor Acres broilers were subjected to 3 dietary treatments (27 pens; 16 birds per pen) for 42 d. The control group was basal diets supplemented with crystalline Lys and DL-Met, and treatment groups had basal diets supplemented with encapsulated Lys and DL-Met at the levels of 80% and 60% of control diets (80CLM, 60CLM), respectively. The growth performance, intestinal development, and transcription of AA transporters were determined. In experiment 2, 24 broiler chickens were subjected to the same treatments as in experiment 1. The plasma concentrations of free AAs were measured 0, 2, 4, and 6 h after feeding. The results showed that 80CLM treatment had no significant influence on production performance, carcass characteristics, and plasma free AAs content during the experiment compared with the control group (P > 0.05). In addition, the 80CLM group moderately enhanced gut morphology development and increased AAs' absorption capacity. However, broilers fed the 60CLM diet had lower production performance and breast muscle weight than the control group (P < 0.05), but increased villi height and B0AT mRNA expression level (P < 0.05). At h 4 after feeding, the 60CLM broilers exhibited higher concentration of Ala, Cys, and total dispensable AAs than the control group (P < 0.05). In conclusion, the result suggests that the supplemental levels of crystalline Lys and DL-Met can be effectively saved approximately for 20% by using the encapsulated form in broilers, with improvements to AAs utilization efficiency, while posing no detrimental effects on production performance. Encapsulated Lys and DL-Met would have greater potential for application when replacing crystalline AAs in broiler chickens.

PSIX-24 Effects of rice feeding on growth performance and protein (amino acids) metabolism in weaning piglets

Abstract This experiment was conducted to clarify the effects of feeding rice on growth performance and protein (amino acids) metabolism in weaning piglets. Sixteen weaning piglets with an average initial weight of 7.5 kg were divided into two groups. One group was fed a corn-soybean meal based diet, and the other was fed a rice-soybean meal diet. Each diet contained about 46% of corn or rice. A 2-week growth trial was conducted and growth performance, dry matter and crude protein digestibility, liver lysine-ketoglutarate reductase activity, plasma urea nitrogen, glucose, insulin, and free amino acids concentrations were measured. The average daily gain (g/d) and feed efficiency (gain/feed) in rice-fed piglets were significantly higher than those in corn-fed piglets. Average feed intake, however, was not significantly different between corn- and rice-fed piglets. Dry matter and and crude protein digestibility were not significantly different between two groups. Liver lysine-ketoglutarate reductase activity tended to be lower (P = 0.073) in rice-fed piglets than that in corn-fed piglets. Plasma urea nitrogen concentration in rice-fed piglets was significantly lower than that in corn-fed piglets. Plasma glucose and insulin concentrations were significantly higher in rice-fed piglets than those in corn-fed piglets. Plasma free valine, isoleucine, tryptophan, and glysine concentrations were significantly higher in rice-fed piglets than those in corn-fed piglets. On the other hand, plasma histidine concentration in rice-fed piglets was significantly lower than that in corn-fed piglets. In conclusion, these results clearly show that rice feeding affects the protein and amino acids metabolism and improves the growth performance in weaning piglets. Rice could be considered to be a good feedstuff for weaning piglets.

Plasma-free amino acid profiles in dogs with hepatocellular carcinoma.

BackgroundMetabolomic analysis using blood samples has been suggested to be useful for the early detection of cancer. Among metabolites, plasma‐free amino acid (PFAA) profiles are potential diagnostic biomarkers for several diseases including cancer. However, the relationship between PFAA concentrations and liver tumors in dogs remains unknown.ObjectiveTo determine the characteristics of PFAA profiles of dogs with hepatocellular carcinoma (HCC) and correlated clinical features.AnimalsThirty‐four client‐owned dogs diagnosed with HCC (n = 26) and benign liver diseases (n = 8) and 11 age‐matched healthy dogs.MethodsProspective study using heparinized blood samples from fasted dogs. Plasma was deproteinized, and the concentrations of 21 amino acids were measured using an automated high‐performance liquid chromatography amino acid analyzer.ResultsPlasma glutamic acid concentrations were significantly different among groups (P < .0024 after Bonferroni correction). Compared to healthy dogs, dogs with HCC and benign liver diseases had significantly higher concentrations of glutamic acid by post hoc analysis. However, no significant difference in the PFAA profiles of HCC and benign liver diseases were detected. In addition, preoperative and postoperative PFAA profiles of dogs with HCC were not significantly different.Conclusions and Clinical ImportanceIncreased glutamic acid concentrations might play a role in the development or be a consequence of liver tumor formation. However, PFAA profiles of HCC could not be differentiated from those of benign lesions. In addition, glutamic acid concentrations did not change after surgical resection. These results indicate that PFAA profiles may not be useful biomarkers for detecting HCC in dogs.

Amino acid derangements in adults with severe falciparum malaria

Amino acid derangements are common in severe falciparum malaria and have been associated with endothelial dysfunction (L-arginine), metabolic acidosis (alanine and lactate), and disease severity (phenylalanine and tryptophan metabolites). Whether these amino acid perturbations reflect isolated pathogenic mechanisms or if they are part of overall changes in amino acid metabolism is unclear. To investigate this, we prospectively simultaneously quantified a broad range of plasma free amino acids (PFAA) using HPLC-MRM-Mass spectrometry in relation to presenting symptoms in adults with severe malaria (n = 88), septicaemia (n = 88), uncomplicated malaria (n = 71), and healthy controls (n = 48) from Bangladesh. The total plasma concentration of measured amino acids was significantly reduced in each of the patient groups when compared to normal levels observed in healthy local controls: uncomplicated malaria −54%, severe malaria −23%, and sepsis −32%, (p = <0.001). Inspection of amino acid profiles revealed that in each group the majority of amino acids were below normal levels, except for phenylalanine. Among patients with severe malaria, L-lactate was strongly associated with an increase of the total amino acid concentration, likely because this reflects tissue hypoxia. Our data confirm previously described amino acid abnormalities, likely resulting from overall changes in the concentration of PFAA.

Partial Amino Acid Metabolism and Glutamine Synthesis as the Ammonia Defensive Strategies During Aerial Exposure in Chinese Loach Paramisgurnus dabryanus.

The Paramisgurnus dabryanus was exposed to air to assess the changes in plasma, liver and muscle free amino acid (FAA) contents. The FAA concentrations in plasma, liver and muscle of P. dabryanus were significantly affected by aerial exposure (P < 0.05). After 12 h of aerial exposure, the plasma glutamate contents increased significantly (P < 0.05) and reached peak value at 24 h of air exposure. With increasing air exposure time, the plasma alanine contents increased significantly and more dramatically than the control values (P < 0.05). From 24 to 48 h of aerial exposure, the liver free glutamate contents increased significantly and reached the peak value at 48 h of air exposure (P < 0.05). The liver free alanine contents in air exposure group were markedly higher than these values in the control group (P < 0.05). After 72 h of air exposure, the muscle free glutamate contents increased markedly (P < 0.05) and were significantly higher than the control values (P < 0.05). The muscle free alanine contents remained at constant values during the first 12 h of aerial exposure (P > 0.05), thereafter, these concentrations increased significantly until the end of experiment (P < 0.05). Our results showed that glutamate and NH4+ could be used to synthesize glutamine via glutamine synthetase to convert internal ammonia into non-toxic glutamine in P. dabryanus during air exposure. Furthermore, the P. dabryanus could catabolize several certain amino acids, leading alanine form to reduce endogenous ammonia production. The decrease in tissue free glutamate, arginine and proline in P. dabryanus indicated that these certain amino acids should be the starting substrate to be converted to alanine and energy.

Genetic basis for plasma amino acid concentrations based on absolute quantification: a genome-wide association study in the Japanese population

To assess the use of plasma free amino acids (PFAAs) as biomarkers for metabolic disorders, it is essential to identify genetic factors that influence PFAA concentrations. PFAA concentrations were absolutely quantified by liquid chromatography–mass spectrometry using plasma samples from 1338 Japanese individuals, and genome-wide quantitative trait locus (QTL) analysis was performed for the concentrations of 21 PFAAs. We next conducted a conditional QTL analysis using the concentration of each PFAA adjusted by the other 20 PFAAs as covariates to elucidate genetic determinants that influence PFAA concentrations. We identified eight genes that showed a significant association with PFAA concentrations, of which two, SLC7A2 and PKD1L2, were identified. SLC7A2 was associated with the plasma levels of arginine and ornithine, and PKD1L2 with the level of glycine. The significant associations of these two genes were revealed in the conditional QTL analysis, but a significant association between serine and the CPS1 gene disappeared when glycine was used as a covariate. We demonstrated that conditional QTL analysis is useful for determining the metabolic pathways predominantly used for PFAA metabolism. Our findings will help elucidate the physiological roles of genetic components that control the metabolism of amino acids.

Methods for Absolute Quantification of Human Plasma Free Amino Acids by High-Performance Liquid Chromatography/Electrospray Ionization Mass Spectrometry Using Precolumn Derivatization.

Plasma free amino acid (PFAA) concentrations in humans are affected by various diseases. However, the variations caused are not dramatic, so a high accurate and precise method for analyzing PFAAs is required. The PFAA analysis protocol described in this chapter covers blood sampling, sample pretreatment, amino acid derivatization, and LC-MS analysis. Each procedure is important for accurate and precise quantification.In the protocol, a human blood sample is collected using an EDTA-2Na or 2K vacuum collection tube and then immediately cooled in water mixed with crushed ice. The sample is then centrifuged on cooling to allow a plasma sample to be removed. A stable-isotope-labeled internal standard solution is added to the plasma, and then the plasma is deproteinized with acetonitrile. The amino acids in the plasma are then derivatized using 3-aminopyridyl-N-hydroxysuccinimidyl carbamate (APDS) reagent which is designed for LC-MS analysis. The derivatized amino acids are separated by reverse-phase HPLC and detected by electrospray ionization mass spectrometry. Using this method, 21 amino acids in human plasma can be analyzed with a 12min cycle. The accuracy and precision are both better than the required criteria given by the US Food and Drug Administration in guidance of Bioanalytical Method Validation.

Effects of dietary supplementation of l-methionine vs. dl-methionine on performance, plasma concentrations of free amino acids and other metabolites, and myogenesis gene expression in young growing pigs.

Methionine (Met), the second or third limiting amino acid (AA) in typical swine diets, plays important roles in promoting swine health and growth, especially, muscle growth. Whereas dl-Met products have been used in swine industry for many years, l-Met products have been developed recently. This research was conducted to study the effects of supplemental l-Met or dl-Met on nutrient metabolism, muscle gene expression, and growth performance of pigs. Twenty crossbred young barrows (initial body weight [BW] 21.2 ± 2.7 kg) were randomly assigned to 20 individual pens and two dietary treatments according to a completely randomized design with pigs serving as the experiment unit (n = 10). Two corn and soybean meal-based diets (diets 1 and 2) were formulated to meet or exceed the recommended requirements for energy, AA, and other nutrients (NRC. 2012. Nutrient requirements of swine, 11th ed. Washington, DC: The National Academies Press; AMINODat 5.0). Crystalline l-Met and dl-Met were supplemented to diets 1 and 2 (both at 0.13%, as-fed basis), respectively. After 4 wk of an ad libitum feeding trial, BW and feed intake were measured to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). Blood samples were collected from the jugular vein for analyses of plasma AA and metabolite concentrations. The longissimus dorsi muscle samples were collected for analysis of myogenesis gene expression. Data were analyzed using Student’s t-test. There were no differences (P = 0.56 to 0.94) in ADG, ADFI, or G:F between pigs fed the two experimental diets and no differences between diets were observed in plasma free AA concentrations. No differences were observed between pigs fed the two diets in expression of mRNA for eight myogenesis-related genes, which were myogenic differentiation 1, myogenin, myogenic factors 5, muscle regulatory factor 4 (a.k.a. myogenic factors 6), and myocyte enhancer factors 2A, 2B, 2C, and 2D. In conclusion, results of this experiment indicate that the bioefficacy of l-Met is not different from that of dl-Met, which is likely because of an efficient conversion of d-Met to l-Met by pigs.

Post-operative AICS status in completely resected lung cancer patients with pre-operative AICS abnormalities: predictive significance of disease recurrence

The AminoIndexTM Cancer Screening (AICS) system, a plasma-free amino acid (PFAA)-based multivariate discrimination index, is a blood screening test for lung cancer based on the comparison of PFAA concentrations between patients with lung cancer and healthy controls. Pre- and post-operative AICS values were compared among 72 patients who underwent curative resection for lung cancer. Post-operative changes in PFAA concentrations were also evaluated. AICS values were classified as rank A (0.0–4.9), B (5.0–7.9), or C (8.0–10.0). Rank B–C patients were evaluated for outcomes and post-operative changes in their AICS values. Twenty-three of the 44 pre-operative rank B–C patients experienced post-operative reductions in AICS rank. Only one patient experienced cancer recurrence. Post-operative changes in PFAA concentrations were associated with the risk of post-operative cancer recurrence (p = 0.001). Multivariate analysis revealed that the absence of a post-operative reduction in AICS rank independently predicted cancer recurrence (hazard ratio: 14.28; p = 0.012). The majority of patients had high pre-operative AICS values and exhibited a reduction in AICS rank after curative resection. However, the absence of a post-operative reduction in AICS rank was associated with cancer recurrence, suggesting that AICS rank may be a sensitive marker of post-operative recurrence.

Plasma-Free Amino Acid Profiles in Crohn's Disease: Relationship With the Crohn Disease Activity Index.

We aimed to clarify the relationship between plasma-free amino acid (PFAA) profiles and the Crohn’s disease (CD) activity index (CDAI) in patients with CD.Methods:We measured fasting PFAA concentrations in 29 patients with CD and their correlation with disease activity.Results:In all patients, significant correlations were noted between CDAI and concentrations of valine, methionine, leucine, histidine, tryptophan, alanine, tyrosine, total amino acids (TAAs), nonessential amino acids (NEAAs), essential amino acids (EAAs), and branched-chain amino acids (BCAAs). In patients with the ileo-colonic type of CD, significant correlations were noted between CDAI and valine, histidine, tryptophan, glutamine, TAA, NEAA, EAA, and BCAA. In ileal type, significant correlations were observed between CDAI and threonine, valine, histidine, serine, and glycine. In colonic type, significant correlations were noted between CDAI and valine, histidine, tryptophan, TAA, NEAA, EAA, and BCAA.Conclusions:In patients with CD, plasma amino acids appear to be associated with disease activity.